Two and three point tractor hitches are well know in which the lower pair of lift arms, in many cases, have a ball type coupling means adjacent the free outer ends thereof. Implements that are to be connected to these arms have a spaced apart pair of lugs that project into a hole in each of respective ones of the balls. Positioning of the tractor hitch relative to the implement must be relative precise in order to couple the implement to the hitch. The implement may for example be a grader blade, a disc mower, a post hole auger or any one of a number of different implements. These are heavy pieces of equipment and therefor not readily moved thereby dictating moving the tractor to precisely position the hitch relative to the implement. Doing this by one's self can often require getting on and off the tractor many times and subject the user to unnecessary inconvenience.
Using hooks extending from the lift arm rather than ball and socket arrangement having holes for the lugs, simplifies connecting the lift arms to the implement but unfortunately many of the known tractor hitches are of the conventional ball type. An object of the present invention therefore is to provide an adapter that converts the lift arm from a ball type to a hook type coupling means. The adapter of the present invention not only quickly and easily converts the ball type connecting means to a hook type coupling means but also has provision for adjustably aligning the adapter relative to the lift arm on which it is mounted.
Hook type connections for hitches are well known and many varieties thereof are exemplified by the teachings of the following United States patents: U.S. Pat. No. 5,713,691 granted Feb. 3, 1998 to G. Solberg; U.S. Pat. No. 5,497,835 granted Mar. 12, 1996 to J. Laubner et al; U.S. Pat. No. 5,441,117 granted Aug. 15, 1995 to N. Fartmann et al; U.S. Pat. No. 5,303,790 granted Apr. 19, 1994 to L. Coleman; U.S. Pat. No. 5,129,667 granted Jul. 14, 1992 to R. Gratton; U.S. Pat. No. 5,050,684 granted Sep. 24, 1991 to J. Vollmer; U.S. Pat. No. 4,241,935 granted Dec. 30, 1980 to J. Vollmer; U.S. Pat. No. 4,944,354 granted Jul. 31, 1990 to H. Langen et al; U.S. Pat. No. 4,773,666 granted Sep. 27, 1988 to R. Koberlein et al; U.S. Pat. No. 4,157,838 granted Jun. 12, 1979 to W. von Allworden; U.S. Pat. No. 4,146,246 granted Mar. 27, 1979 to H. Geisthoff; U.S. Pat. No. 3,977,698 granted Aug. 31, 1976 to W. von Allworden; U.S. Pat. No. 3,791,456 granted Feb. 12, 1974 to J. Koch; U.S. Pat. No. 3,489,431 granted Jan. 13, 1970 to C. McKeon et al; and U.S. Pat. No. 2,295,021 granted Sep. 8, 1942 to D. Weiss.
The foregoing patents disclose variously constructed hitch hook couplings that normally include an upwardly facing open mouth hook and a spring loaded latch for releasibly holding a member captive in the bite of the hook.
U.S. Pat. No. 5,544,708 granted Aug. 13, 1996 discloses a pair of hook members interconnected by a spreader bar and each have an open channel for receiving respective ones of the pair of tractor hitch lift arms. The spreader bar has pins of reduced size that pass through aligned holes in the lift arms and a channel member (or box section) that projects from the hook member. The spreader bar is adjustable in length and spaces the lift arms a preselected distance from one another. Securement pins retain the lift arms on the spreader bar pins. FIG. 6 illustrates an embodiment wherein a pin is fixedly secured to the channel member alleviating the need for a spreader bar and it is contemplated that separate pins could also be used with the embodiment illustrated in FIG. 7 thereby avoiding the use of the spreader bar.
One of the drawbacks of the foregoing embodiments of the '708 patent is that the mounting channel, or box section as the case maybe, is offset from the implement connecting hook portion thus not only complicating the construction but also reducing the strength thereof. Also the channel as well as the box mounting portion is such that the assembly follows the path and is an extension of the diverging arms with the result the hooks would be spaced from the structure of the machine on which the pegs are mounted and projecting. The structure has no means of adjustably positioning the hook assembly relative to the hitch lift arm on which it is mounted.